The Crime Prevention Website


These paragraphs consider the security requirements for timber, single leaf back and side doors that are not used as a main entrance. It is assumed that these doors open into a private garden and are in a single family dwelling house.  It is further assumed that you are going to keep the door.  Further information about door locks and hardware can be found in  Door locks, hardware and fittings .

During the day when people are at home these doors are often left unlocked.  This happens because the door doesn’t normally self lock and residents feel confident that as the door opens into a private garden with adequate fencing and a locked garden gate, things should be OK.  (See  Preventing crime in the garden outbuildings and garage,  Garden boundaries     I go along with those thoughts, but at night, when I’ve settled down to watch a movie on the box, I do turn the key in the lock to be on the safe side.  When we retire to bed I take the key out and leave it somewhere where the entire household can find it (in case of emergencies).      

Minimum security requirements

The following bullet points indicate the minimum security requirements for a timber door that should satisfy your insurance company’s requirements, but you  must  check with them first.

  • The door should be at least 44m thick to allow for the installation of mortice locks and to provide resistance against forcing
  • It should be hung on three hinges
  • The frame should be secured to the brick or block with screws or frame fixers at maximum centres of 600mm and within 300mm from each corner.  You may not be able to identify the fixing points on an old door frame
  • The door should be fitted with the following locks: A mortice sashlock certificated to BS 3621 positioned near to the centre of the door and a pair of key operated mortice security bolts fitted at right angles to the grain of the wood either bolting into the side frame or into the top  and bottom frames, but make sure that everyone in the house can operate them
  • A pair of hinge bolts should be fitted if the door opens outwards; and most do
  • A door viewer if you do not have clear glass in the door
  • If the door has a thin plywood panel or glazed panel in the bottom half of the door it can be easily kicked in.  This can be improved by fitting a 12mm waterproof plywood panel over the outer face of the existing panel.  The new panel should be glued and screwed in place and should overlap the rails and stiles.  Paint to match

New plywood panel fitted over existing thin plywood panel on back door  

Additional security measures

The following additional security measures can be added if you live in an area with crime risks higher than the average

  • A security grille can be fitted to the back of a glazed panel to prevent access through the glass.
  • Ordinary glass in a glazed panel can be replaced with 6.4mm or thicker laminated glass (See  Glazing for domestic security
  • If the door opens inwards reinforcing bars can be fitted on the inner face of the hinge and locking frames
  • Reinforcing plates can be fitted on either side of the mortice sashlock
  • It may be possible to install collapsible gates behind these doors. (See Security shutters, grilles and gates )